Creamy, tangy, and packed with plant-based protein, this lightly mashed lentil sandwich filling is as simple as can be. Pickled red onions and mustard provide a sharp, savory kick, brought together with your favorite vegan mayo.
Lightly or fully mashed legume sandwiches have quietly become a lunchtime mainstay—probably the meal I pack for work more often than any other.
There is so much that I love about them:
- Convenience: These sandwiches are easy to pack, they hold up nicely in my lunchbox, and they’re not messy to eat at my desk. I don’t have to worry about stray bits of food escaping my fork and landing onto my keyboard.
- Versatility: Swapping in different legumes, different crisp, diced vegetables, minced fresh herbs, or varying sources of acid (lemon, vinegar, or in this case, pickled onion brine) can transform the recipe template.
- Nutrition: There’s satisfaction in knowing that I’ve tucked a serving of beans or lentils—along with all of their plant protein, fiber, and micronutrients—into an effortless midday meal, no matter how busy the week is or how little time I’ve had for meal prep.
For years, I almost always defaulted to chickpeas or white beans for these kinds of sandwiches. Recipes like my vegan chickpea “tuna” salad with artichoke hearts and smashed garlic tahini white beans have lived on heavy rotation in my kitchen, and they remain favorites.
Lately, though, I’ve started turning to lentils just as often. Beyond helping me to vary my legume rotation, their smaller size is especially well-suited to a sandwich filling: you can lightly mash them with minimal effort, which cannot be said of chickpeas!
They result in a nice, soft sandwich that nevertheless has texture.
Letting Condiments Do the Heavy Lifting
One of my favorite low-lift cooking strategies is leaning on flavorful condiments. The right ones deliver enough seasoning to save you the effort of measuring out multiple spices, vinegars, or aromatics. In my easy chickpea burrito bowls, for example, a few spoonfuls of prepared salsa do the work of a whole spice blend—and spare you from having to chop an onion—with zero extra effort.
Here, a scoop of tangy pickled red onions plays a similar role. Between their bright, briny flavor and a spoonful of Dijon mustard, the filling becomes well-seasoned in an instant.
Vegan mayo, meanwhile, lends a creamy texture and helps to mellow out the tart flavors. I use my homemade cashew mayonnaise, but any store-bought vegan mayo of your choice will work well.
Key Ingredients & Simple Swaps
- Brown or green lentils: Standard brown or green lentils are my go-to. I’m also a big fan of Pardina lentils—a brown variety that’s smaller and rounder than conventional brown lentils—and they work nicely in the sandwich filling. I find that both French green and black lentils are a bit too firm and small to mash effectively in this recipe, while red lentils become too mushy.
- Vegan mayo: If you prefer an alternative or don’t have vegan mayo at home, you can swap in 6 tablespoons of tahini thinned with a tablespoon or two of water.
- Quick pickled onions: I consider these a must for acidity, subtle sweetness, and crunch. While additional pickled vegetables—like pickled shredded carrots or traditional dill pickles—are nice additions, they won’t add the savoriness that onions will. If you don’t have a red onion at home to pickle, yellow onion, white onion, or shallots work just as well.
- Chopped celery: This provides another layer of crunch in the soft mash. I like the flavor of celery in a sandwich filling, too. If you’re not a celery person, try finely chopped cucumber or grated carrot instead.
- Soft sandwich bread & butter lettuce: This is my favorite way to serve the filling. With that said, it’s equally good scooped onto toasted bread open-faced, tucked into a wrap or pita pocket, or served alongside crackers.
A Note on Texture
The only small technical detail that matters in this otherwise simple recipe is removing excess moisture from the lentils.
After boiling the lentils until tender, drain them thoroughly and spread them onto a baking sheet lined with paper towels or a clean tea towel. Lentils hold onto a lot of cooking water; draining them on the towels will ensure that your filling isn’t too liquidy once the mayo is added.
Easy Lentil Sandwich Filling
Ingredients
For the sandwich filling:
- 1 cup brown or green lentils (200 g)
- 1/2 cup homemade vegan mayo with cashews (or your favorite store-bought vegan mayonnaise; you can also substitute 6 tablespoons of tahini + 1-2 tablespoons of water)
- 1 tablespoon Dijon mustard
- 1 large stalk celery, finely chopped (or two smaller stalks)
- 2/3 cup finely chopped 10-minute quick pickled onions (adjust the amount to taste)
- Freshly ground black pepper, to taste
To serve:
- 8 slices soft, whole grain or white sandwich bread (substitute rye, pumpernickel, sourdough, or another favorite sandwich bread)
- Butter lettuce leaves
Instructions
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Bring a pot of water to a boil. Add the lentils. Turn the heat to medium low, then simmer them for 25-35 minutes, or until they're tender but not overly mushy. Taste a few lentils after 25 minutes of cooking to ensure that you don't overcook them.
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Drain the lentils. Line a baking sheet with paper or tea towels, then spread the cooked lentils over it. This step helps to remove excess moisture from the lentils, so that the filling doesn't become watery. Allow the lentils to drain and cool for 10 minutes.
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Transfer the lentils to a mixing bowl. Add the mayonnaise and mustard. Use a wooden spoon to mix the lentils thoroughly, mashing them up a little as you go. Fold in the celery and pickled onions, then taste the mixture and add freshly ground black pepper and salt as needed. You can be relaxed with this recipe: add extra chopped pickled onions or regular dill pickles, grated carrot, chopped nuts, or herbs of your choosing.
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To make sandwiches, spread the lentil mixture over four pieces of soft sandwich bread, then top with butter lettuce leaves and another slice of bread. The filling makes a generous amount, so you may have enough for five sandwiches depending on the size of your bread! Slice the sandwiches in half and serve.
Video
Notes
I hope that this humble sandwich will become as indispensable to you as it has to me, especially during hectic weeks when cooking isn’t a priority, but good lunchtime nutrition is. Enjoy!
xo
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